This invention pertains to an improved method and means for rapidly determining the operational status of a film processor, such as an x-ray film developer. More particularly, this invention pertains to such means and method wherein the proper operation of the developer or identified malfunctions of the developer can be confirmed reliably and efficiently.
With the increasing concern for minimizing x-ray exposure, the need has grown for quickly and accurately determining whether an x-ray developing apparatus or processor is functioning properly. If it is not, the x-ray may have to be retaken.
To a less extent, method and means for determining the operational status of other types of film processors would also be desirable. For that reason, the present invention will be described herein with reference to photograhic film and film processors generally, although the most immediate and well defined need to which the present invention is addressed is that involving x-ray film processing.
In developing photographic films, it is important to closely monitor a number of critical parameters, such as for example, the temperature and strength of the chemical developers employed, to insure that the proper film densities are achieved. It is sometimes possible to determine that one or more of these parameters is not correct by inspection of a normally developed film, but without more information, identification of the specific cause of improper processing is difficult.
Manual comparison of a developed film (produced from calibrated exposure of sections of the film) to predetermined density standards and analysis of the results of this comparison (sometimes requiring trial and error adjustments of the processor) is presently relied upon to determine the operational status of x-ray film processors in some hospitals. The general object of the present invention is to provide a method and apparatus for performing this function automatically.
The only known prior art method and means for performing such function automatically is that disclosed and claimed in U.S. Pat. No. 3,995,959 of Gary S. Shaber, one of the co-inventors herein. That patent discloses and claims a system wherein a film having a test pattern including at least three areas of graded density, one of which is an unexposed or base fog area, is developed in the processor to be checked. The developed film is then tested in a device including three light sources and photo detectors focused on the three graded density areas (the proper graded density of which is predetermined and related to a preselected signal in the photodetector associated with that area) in order to determine whether each graded density area, as developed, is too light or too dark or within the specified limits.
Various combinations of the output indications for the graded density areas being too light, acceptable, or too dark are electronically integrated to produce output signals indicative of either proper operation of the processor or specified malfunctions of the processor such as "developer underreplenished", "developer temperature too low", "developer temperature too high", and "developer contaminated".
The apparatus disclosed for carrying out that process in the '959 patent is somewhat inefficient, however, because of the continuing necessity to maintain the relative calibration of the various light sources and photodetectors and the necessarily duplicative circuits in the device.
It is therefore a general object of the present invention to provide a more efficient and more reliable method and means for determining the operational status of a film processor utilizing evaluation of a plurality of graded density test areas in a developed film, comparison of these graded densities to preselected standards and interrelating the results of that test to confirm proper process or operation or specific problems in the processor.
A more specific object of the present invention is to provide an expeditious method, means and film strip design adapted to indicate, very rapidly, the operational status of an x-ray film processor.